This invention relates to a failure warning system of an electric power unit in a vehicle.
FIG. 4 is a circuit diagram of the prior art showing a conventional failure warning system of an electric power unit in a vehicle. FIG. 5 is a control characteristic chart showing the relationship between the duty ratio of duty signal and control voltage of a generator.
In FIG. 4, an electric power generation unit (ACT) 1 comprises a generator 2 having a stator winding 2a and a field winding 2b, a field current controller 3, and a rectifier 4 for rectifying alternating voltage occurring at the stator winding 2a to DC voltage. A noise prevention capacitor 5 for preventing noise to a radio, etc., is connected to an output terminal A of the rectifier 4.
The field current controller 3 is configured as follows: A transistor 3a has an emitter grounded via a ground line E and a collector connected via a connection line F1 to the field winding 2b for intermittently controlling a field current flowing into the field winding 2b. A free-wheel diode 3b is connected to the field winding 2b in parallel via connection lines F1 and F2 for suppressing surge voltage caused by intermittent field current by the transistor 3a.
A voltage detector 3c detects an output voltage of the rectifier 4 and the detection result is input to a voltage controller 3d. A 1-phase voltage of the generator output winding 2a is input via a connection line P1 to the voltage controller 3d for detecting a voltage of power generated by the generator.
A duty signal DC is input to a duty detector 3e via a terminal C and a connection line C1 from a high-voltage load controller 11 (described below). The duty detector 3e detects the duty signal and outputs a power voltage indication signal to the voltage controller 3d.
A diagnosis section 3f diagnoses integrity of the generator 2, for example, checks to see if an error such as no electric power generation or overvoltage exists. The field current controller 3 also includes a power supply 3g, a power drive 3h, a power on/off transistor 3j, and a transistor 3k brought into conduction when the diagnosis result of the diagnosis section 3f is abnormal for turning on an alarm lamp 10 (described below) via a terminal L. Operation power of the field current controller 3 is supplied from a battery 7 (described below) via an S terminal and a connection line S1.
A change-over switch 6 has a common contact 6c, a normally open contact 6a, a normally closed contact 6b, and an excitation coil 6d. The common contact 6c is connected to an output terminal A of the rectifier 4 via a terminal A and a connection line A1. The normally open contact 6a is connected to an electrically heated catalyst carrier 14 (described below) by a connection line H1 via a terminal H. The normally closed contact 6b is connected to the positive electrode of the battery 7 (described below) via a connection line B1.
The excitation coil 6d is connected between terminals B and D and the terminal D is connected to the high-voltage load controller 11 (described below) via a connection line D1.
A storage battery 7 and a general load 8 of headlights, etc., are connected to the output terminal A of the rectifier 4 via the terminal B of the change-over switch 6, the normally closed contact 6b, and the connection line A1. Vehicle system voltage, normal voltage (in this example, 12 V), is supplied from the generator 2.
A key switch 9 is connected in series with a pilot lamp 10 and is connected to the positive electrode of the battery 7 and a terminal L of the electric power generation unit 1 via a connection line Ig1.
The high-voltage load controller 11 receives information such as the number of revolutions of an engine via a connection line EN1 from an engine controller 12 and instructs the engine controller 12 to turn the engine over a connection line EN2. It also detects the on state of the key switch 9 over a connection line Ig2.
Also, the high-voltage load controller 11 is connected to the terminal D of the change-over switch 6 via the connection line D1 for controlling the excitation coil 6d of the change-over switch 6. Further, it detects terminal voltage of a heater 14a of the electrically heated catalyst carrier (EHC) 14 (described below) via a terminal H and a connection line H2. It also detects temperature of the heater 14a of the EHC 14 by a temperature sensor 14b via a terminal T and a connection line T1. An indicator lamp 13 is connected to a terminal W.
The high-voltage load controller 11 transmits duty signal DC, which is a control signal of periodic pulse, to the field current controller 3 via the terminal C and the connection line C1. The generator 2 is controlled in response to the duty ratio DU of the duty signal DC (this topic will be discussed in detail below):
0.ltoreq.DU&lt;15 [%] normal voltage control zone PA1 15.ltoreq.DU&lt;30 [%] power generation stop zone PA1 30.ltoreq.DU&lt;100 [%] high-voltage control zone
where the duty ratio DU of the duty signal DC is represented as percentage of the pulse width to the pulse period.
The electrically heated catalyst carrier (EHC) 14 has the metallic heater 14a, which also serves as a catalyst carrier, connected between the Normally open contact 6a of the change-over switch 6 and ground via the connection line H1, and high voltage (in this example, about 30 V) is applied. The EHC 14 is provided with the temperature sensor 14b for detecting an arrival point in time to active temperature of a catalyst of the heater 14a (about 400.degree. C.), overheat thereof, etc.
A normal voltage circuit 15 is a circuit containing the battery 7 and the general load 8; normal voltage is applied. A high-voltage circuit 16 is a circuit containing the EHC 14; high voltage is applied.
In the electric power generation unit 1 thus configured, vehicle system voltage of about 12-14 V, normal voltage, is applied to the battery 7, the general load 8, the connection lines D1, B1, S1, IG1, etc. High voltage of about 30-40 V is applied to the heater 14a and connection line H1 of the EHC 14, the contact 6a of the change-over switch 6, etc.
When the generator 2 runs at a normal voltage, normal voltage is applied to the stator winding 2a and field winding 2b of the generator 2, the rectifier 4, the noise prevention capacitor 5, the common contact 6c of the change-over switch 6, the connection lines A1, P1, F1, and F2, the terminal A, etc.; whereas when the generator 2 runs at a high voltage, high voltage is applied thereto.
In operation, first when the ignition switch 9 is turned on and further a starter switch (not shown) is turned on, the engine (not shown) starts turning and at the same time, the generator 2 also starts turning. At the time, the normally closed contact 6b of the change-over switch 6 is connected to the common contact 6c for supplying an initial excitation current from the battery 7 to the field winding 2b of the generator 2.
At the time, duty signal DC, for example, of duty ratio 10% is sent from the high-voltage load controller 11 to the field current controller 3 and the generator 2 starts power generation at the vehicle system voltage 12.8 V, normal voltage. Immediately after it, duty signal DC of duty ratio in the power generation stop zone, for example, duty ratio 20% is sent from the terminal C of the high-voltage load controller 11, causing the generator 2 to change to the power generation stop (no charge) mode.
Further, the excitation coil 6d of the change-over switch 6 is excited via the terminal D by the high-voltage load controller 11 with a given time delay (about one second) and the normally open contact 6a and the common contact 6c are connected for switching the output terminal A of the generator 2 to the EHC 14. After this, with a given time delay (about one second), the high-voltage load controller 11 sends duty signal DC, for example, of duty ratio 75% in a preset high voltage control zone to the field current controller 3 through the terminal C, thereby changing the generator 2 from the no charge mode to the high-voltage power generation mode for controlling the generator voltage to about 30 V in response to the duty ratio 75% through the duty detector 3e and the voltage controller 3d.
The temperature sensor 14b of the EHC 14 detects the timing at which the heater 14a reaches the active temperature of the catalyst and power supply becomes unnecessary. When the power supply to the EHC 14 becomes unnecessary, the high-voltage load controller 11 transmits duty signal DC, for example, of duty ratio 20% for placing the generator 2 in the no charge mode to decrease the output current to the EHC 14 or bring it to almost zero in order to prolong the contact life of the change-over switch 6 and prevent semiconductor devices from being destroyed due to surge voltage generated by load cutoff of the generator 2.
Then, the common contact 6c of the change-over switch 6 is switched to the normally closed contact 6b for connecting the output terminal A of the electric power generation unit 1 to the normal voltage circuit 15 containing the battery 7.
Further, with a given time delay (about one second), the high-voltage load controller 11 sends duty signal DC, for example, of duty ratio 0% to the field current controller 3 for placing the generator 2 in the normal voltage power generation mode to generate power at 14.4 V.
The high-voltage load controller 11 is provided with the terminal H to detect voltage applied to the EHC 14 and a terminal T for the temperature sensor to detect temperature of the heater 14a for detecting an abnormal condition in the high-voltage circuit 16, such as a broken line, short circuit, or overheat of the heater 14a of the EHC 14, over the connection lines H2 and T1. When detecting an abnormal condition, the high-voltage load controller 11 turns on or blinks the indicator lamp 13 connected to the terminal W of the high-voltage load controller 11 for giving a warning of the abnormal condition to the vehicle driver, etc. Further, it uses the diagnosis section 3f for detecting an abnormal condition of power generation of the generator 2, such as no power generation or high voltage of the generator 2 detected over the connection line P1, and turns on or blinks the pilot lamp 10 connected to the terminal L of the field current controller 3 of the electric power generation unit 1 for giving a warning of the abnormal condition to the vehicle driver, etc.
The high-voltage load controller 11 may change the duty ratio of the duty signal DC for controlling the voltage of the generator 2 in response to the duty ratio. For example, it changes the duty ratio of the duty signal DC in the range of 0% to 15% for controlling the normal voltage supplied to the normal voltage circuit 15 in response to the duty ratio. In FIG. 4, it may instruct the field current controller 3 to control the voltage to 14.4 V in the range of 0%-5% and 12.8 V in the range of 5%-15%. Likewise, it can also transmit duty signal DC of duty ratio 30%-100% for controlling the voltage supplied to the high-voltage circuit to 12.8-40 V in response to the duty ratio.
Since the conventional warning system of an electric power unit in a vehicle is thus configured, two lamps of the pilot lamp 10 and the indicator lamp 13 must be provided for failure alarms of the power unit and wiring is required for each of the lamps, leading to high costs and an increase in the installation space.